View Program - 63rd Annual Drosophila Research Conference

New species originate when diverging populations become reproductively isolated and morphologically distinct. In theory, genetic correlation between the two phenotypes through pleiotropy or partial linkage significantly accelerates speciation. Here, we investigate the genetic correlation between mate choice and pigmentation difference in a pair of sibling species, Drosophila yakuba and D. santomea. We introgressed the “light” phenotype of D. santomea into the “dark” background of D. yakuba through a series of backcrosses. Two introgressed “light”yakuba strains that slightly differed in the degree of pigmentation were obtained. Genome sequencing revealed that the darker of the two strains had two introgressed X-linked loci, each centered on a melanin-synthesis gene, namely yellow and tan. The lighter introgressed strain had, in addition to the two X-linked loci, a third introgressed locus on autosomal arm 3L. The third locus centered on the transcription factor Grunge, which regulates the expression of the melanin-synthesis genes ebony and tan in D. melanogaster. We then conducted reproductive isolation assays between the two introgressed strains and strains from the parental species, measuring male and female mating latency and choice. We found no evidence for reproductive isolation in the darker introgressed strain, in contrast to the lighter strain, which exhibited decreased male mating success most likely due to increased latency. Those findings indicate that reproductive isolation and pigmentation difference between D. yakuba and D. santomea are partly linked through a single autosomal locus. Future dissection of this locus will elucidate the molecular underpinnings of such partial correlation in this primary model of speciation research.

A locus affecting pigmentation evolution and male mating success between two sibling species in Drosophila